Residence Time Distribution (RTD) is a frequently used tool in conventional process equipment and it provides internal flow characterisation by simple tracer tests. In this paper, we explore the feasibility of using RTD to identify fluid distribution uniformity in millimetric multichannel devices. Both theoretical modelling and experimental implementation are conducted to 16-channel systems. Theoretical modelling confirms the effectiveness of non-intrusive RTD measurements in evaluating flowrate distribution uniformity. Different influencing factors, such as channel corrosion, blockage, distributor structure, channel length or width variation, etc., can be reflected by RTD response curve. The experimental setup consists of a lab-developed RTD test platform coupling a fast camera and two miniflowcells capable to quantify rapid tracer concentration evolution through carbon ink visualization. The platform is particularly powerful for very narrow RTD measurement with residence time down to 1 s. With the platform, we investigate the RTD characteristics of a multichannel device under several flow conditions. Model correlation of the experimental data gives valuable information such as fluid distribution, plug-flow ratio and perfectly mixed volume.